Much of the focus will likely be on players like Cristiano Ronaldo, Xabi Alonso, Mario Gomez and Arjen Robben in the second leg of the Champions League semifinal between Real Madrid and Bayern Munich. However, it is very likely that players who start the game on the bench will have the biggest hand in the result.

Real Madrid and Bayern Munich are unquestionably two of the most talented squads in the world, but that talent doesn't end with the first team. Both teams have substitutes that most other clubs would do anything to have as centerpiece players. Therefore, they have the luxury of bringing in fresh, world-class stars when other players are tired.

Here are three top-flight subs who will have a massive impact on the result of a must-win, second-leg match for Los Blancos against FCB.

Which substitute will play the biggest role in the match?

KakaThomas MullerMarceloSubmit Votevote to see results

Which substitute will play the biggest role in the match?

Kaka

79.6%

Thomas Muller

16.7%

Marcelo

3.7%

Total votes: 162

After an extremely rough 2010/11 season, Real Madrid midfielder Kaka has enjoyed a bit of a renaissance this season as a reserve. He has appeared in 26 games as a starter or substitute and has racked up five goals and seven assists. He hasn't been utilized over the past couple of games, but he should be fresh and fit, so there is a good chance that we'll see him as a late sub if Los Blancos need some offensive spark.

Madrid is in a tough spot after losing the first leg because it absolutely must win. With that in mind, all signs point to Bayern Munich playing a strong road game, maintaining shape and emphasizing defense. That means that all of the onus will be on Los Blancos' offense to score at least once. If they can't break through in the first half, it will be all hands on deck in the second. Kaka may not be the same player he once was, but he has the skill and creativity to play a major role.

Thomas Muller

Doug Pensinger/Getty Images

Bayern Munich star Thomas Muller has largely been splitting time with Bastian Schweinsteiger, but their recent rotation dictates that Muller will begin the match against Real Madrid on the bench. Muller came on as a substitute in the first leg vs. Los Blancos and provided a spark that eventually led to Bayern picking up the victory. Muller's form is fantastic and there is little doubt that he will end up on the pitch at some point.

Muller is more of an offensive threat than anything, so he'll come into play more if Madrid finds a way to grab the lead in the game. Provided Los Blancos are able to score at all and gain a lead, the pressure immediately shifts to Bayern Munich because of Madrid's advantage in away goals. Muller's stats of four goals and seven assists on the season aren't overwhelming, but he brings a completely different dimension to the team because of his skill.

Marcelo

Manuel Queimadelos Alonso/Getty Images

Marcelo has been an important player off the bench for Real Madrid all season long, and every indication is that he'll be needed against Bayern Munich. Los Blancos like to take a midfielder out and replace him with Marcelo late in games generally to protect leads, so Marcelo's usage will likely depend largely upon how Madrid fares on the scoreboard.

Real Madrid's objective in this game has to be to strike first and then hang onto the lead. All Los Blancos need is a 1-0 victory, and they will sell out to get it. If Madrid is able to get that all-important goal, then Marcelo will play a key role in the second half. Bayern Munich will be throwing everything it has at the Real Madrid defense at that point, so Marcelo will have to enter the match ready to play and willing to make the tough and dirty plays.